The invention relates to an overlay for a mattress or other support surface incorporating individual foam springs.
It has been known to provide overlays for mattresses and other support surfaces which include a foam pad with convoluted foam elements. The overlay is placed between the bottom sheet and mattress for support and comfort. When the cushion is used in medical applications, strategic pressure relief may also be obtained. Typical foam mattresses or overlays of the convoluted type are disclosed in U.S. Pat. No. 4,686,725. Other foam pads having convoluted foam elements that are truncated are disclosed in U.S. Pat. Nos. 4,673,452; 4,603,445; and 4,686,724. Various designs of these mattresses are typically constructed on a convoluter machine and the shape of the mattress elements may be determined by interchanging the rings of the convoluter machine. The convoluter machine takes a single blank of foam and cuts two mattress pads out of the blank. The problem arises in that a large amount of foam material is taken out of each individual pad due to the nature of the process. The result is that two convoluted foam mattresses are provided with limited cushioning and support as compared to the original foam blank due to the removal of foam material from each pad. For example, a 2 inch convoluted mattress pad requires a 21/4 inch foam blank, and 2 convoluted pads are produced from the blank. However, only about 50 percent of the foam material of the original 21/4 inch blank is in each pad. Due to this technique, there are considerable void spaces in the convoluted mattress and its cushioning ability is limited. The convoluted material tends to bottom out or flatten when laid upon. If it is desired to truncate the convoluted elements so that they are not as pointed, even more foam material is lost. To compensate, a higher density foam is needed. Since this is expensive, numerous types of filler materials have been used to enhance the cushion and support ability of convoluted pads. Another shortcoming of the convoluted type mattress overlay is that the convoluted elements are significantly interconnected together which makes it practically impossible for the convolutions to effectively act as individual spring elements.
It is also known to saw-out foam material to make mattress overlays. For example, it has been known to saw a foam blank into laterally extending form elements with slots in between. The lateral foam elements are then cut longitudinally and separated. From a cross-sectional view, the lateral elements in the center of the pad are wider than the lateral elements on the ends. Approximately 95 percent of the foam material is left in this type of mattress.
U.S. Pat. No. 4,383,342 discloses a molded mattress construction in which essentially all the foam material put into the product remains.
Accordingly, an object of the invention is to provide a foam overlay which primarily provides maximum support and comfort while secondarily provides maximum redistribution of body weight and pressure.
Accordingly, another object of the invention is to provide a mattress or cushion overlay having individual foam springs in which almost all of the foam material remains in the overlay.
Another object of the invention is to provide a foam overlay and method for a mattress or cushion having a plurality of foam springs which act individually and together as spring elements.
Another object of the invention is to provide a mattress or cushion overlay with individual foam springs which may be used to relieve pressure at strategic pressure points of a patient, in addition to providing comfort and support.
Another object of the invention is to provide a mattress or cushion overlay with individual foam springs which are arranged in such a manner that they act individually without interference from each other and act in groups to support heavier body portions in providing pressure relief and other comfort and support functions for patient and normal bed rest.